Historically, there have been a number of options for the permanent removal of hair. Electrolysis has been the most commonly selected approach, in which an operator, usually a electrologist, attaches an electrode to each individual hair shaft, with the patient typically holding a second electrode. An electrical current is then passed through the hair shaft and the hair follicle through the papilla. This precisely directed current can induce permanent injury in the follicle and papilla, stopping the future production of the hair shaft.
Problems exist with the electrolysis technique, however. The success with which hair is permanently removed varies greatly from patient to patient. Moreover, the process is slow since each hair follicle must be individually treated, and there is some discomfort associated with the electric current.
The removal of hair using lasers is another approach that has found only limited success. Numerous techniques have been taught in the prior art. Each, however, suffers from drawbacks such as poor ultimate success in stopping hair growth even after multiple treatments, excessive injury to the tissue surrounding the hair follicles and papilla, and excessively large and expensive laser systems.
One approach relies on a pulsed laser source and the use of an exogenous absorber. A commercially available hair dye solution is first applied to the skin containing the unwanted hair and allowed to migrate along the hair shafts and into the follicles. The skin is then irradiated with a spot size of approximately 0.5 centimeters using a Q-switched YAG laser, or other short pulsed laser system. The pulse durations used by the lasers tend to be short, 15 nsec for the Q-switched laser. It appears that the sub-microsecond pulse durations shocks the hair follicle, which stops hair production, but only for a limited time. After months, the follicle again begins to produce hair, requiring further treatments or other techniques to yield any lasting success.
Other approaches have been proposed that rely on flashlamps, instead of lasers. This has the advantage of a less expensive, reasonably portable light source, but flashlamps create their own control problems. It is difficult to deliver light from the flashlamp to the skin, so that it must be placed in proximity to the skin. The reflectors that surround the flashlamp and collect the light and direct it to the skin must be precisely built and calibrated. Any error can cause hot spots in the spatial energy distribution. This can lead to under-treatment in some areas and burning in others. Moreover, the bandwidth of the light from these flashlamps is broad, usually including the visible and stretching into the longer infrared wavelengths. These longer wavelengths are well absorbed by water that occupies the skin. Thus, the light from these sources tends to penetrate very poorly, which leads to higher fluence levels to sufficiently treat deeper-lying hair producing structures with the concomitant risk of burning or damaging the skin.
Still other approaches use laser light delivery systems that inject light into only a single hair follicle at a time. These have the advantage of a reduced concern for damaging tissue between hair follicles but have many of the same disadvantages associated with the electrolysis. That is, each individual hair and hair follicle must be separately treated.
Long pulse ruby lasers have recently been used in hair removal. The high energy ruby lasers, however, are generally large, inefficient types of laser light generators, when very long pulses are generated.
The present invention is directed to a long pulse alexandrite laser hair removal system. The use of an alexandrite in the present invention allows operation in the near-infrared, specifically in a 100 nm range surrounding 760 nm, and ideally at approximately 755 nm and a surrounding 50 nm range. Infrared in this range allows good penetration while still achieving an acceptable ratio of hemoglobin to melanin absorption. Moreover, the use of a long pulse alexandrite laser, in contrast to short-pulse Q-switched laser typically used on pigmented lesions and tattoos, yields two advantages: 1) the pulse duration now can match the thermal relaxation times of the targeted hair structures within the skin; and 2) the removal of the Q-switching element makes a laser system that is less temperamental and easier to operate.
In specific embodiments, it is desirable to use an index-matching application on the skin sections to be treated. This substance covers the epidermal layer to provide better coupling of the laser light into the skin.
In other aspects of the embodiments, a topical indicator is also preferably used on the skin. Skin irradiation in the near-infrared generally does not produce any characteristic skin color change as is found when using dye pulsed lasers, for example. Thus, it is difficult to know exactly what portions of the skin have already been irradiated during a treatment session. The visual indicator is thermo- or photo-responsive or otherwise responsive to the laser light pulse to generate a visible change. This provides the operator with a record of those parts of the skin that have already been treated.
The skin is preferably treated with laser pulses of greater than a millisecond, preferably approximately 5 to 50 msec. Each pulse should contain a fluence of between 10 and 50 Joules per square centimeter (J/cm2). During each treatment session, each treated section of the skin is preferably irradiated with one such pulse, although multiple pulses could be used. Even so, permanent and complete laser removal may require three to four repeat treatment sessions, with weeks to months long dwell times between each session.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.